Issue 53

A. Moulgada et alii, Frattura ed Integrità Strutturale, 53 (2020) 187-201; DOI: 10.3221/IGF-ESIS.53.16

Figure 11: Variation of the maximum normal stresses  yy according to the various loadings This figure shows that the effect of the repair by composite patch is very distinct; given the gain in the stresses, which experienced fairly low values relative to those found for the cracked plate without repair, therefore the composite patch is a damper or a stress absorber. The reduction of the stresses is very distinct for this not repaired plate by the effect of the repair by the two patches and it is very remarkable and more effective for the boron/epoxy, which presents better results for the reduction of the stresses and to prolong the service life of repaired materials. Integral J For the variation of the integral J as a function of each sequence (Plaice) for different loading for the plate repaired by patch in composite which is (Carbon / epoxy), we notice that as the load increases, the corresponding integral J also increases, and this integral reaches its maximum at sequence No. 2, that is to say for the orientation of the fibers at 45 °, and this maximum value is of the order 5.3mj / mm 2 .

20MPa 40MPa 60MPa 80MPa 100MPa

20MPa 40MPa 60MPa 80MPa 100MPa

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Integrale J

Integrale J

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Carbon epoxy sequences

Boron epoxy sequences

Figure 12: Representation of the integral (J) for different loading.

For the plate repaired by patch in composite (Boron epoxy), the variation of the integral J for different loads for the four stacking sequences is almost proportional to the loading, since for low loads such for 20MPa and 40MPa, this integral does not exceed 2.7mj / mm 2 , and reaches its peak which is of the order of 7.5 mj/mm 2 for the same sequence with the orientation of the fibers at 45 °, which corresponds to the second fold of the boron epoxy composite. in the close vicinity of the adhesive, the energy due to crack propagation, induces a greater intensity and for progressive loads and decreases towards the last stacking sequences of the patch, according to shows that the patch absorbs a very large amount energy that passes through it, and consequently, increase the lifetime of the structure.

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